package com.LeeCode;

/**
 * 正则表达式匹配
 */

public class Code010 {
    public static void main(String[] args) {
        String s = "ab", p = "ab*";
        System.out.println(new Code010().isMatch(s, p));

    }

    public boolean isMatch(String s, String p) {
        int m = s.length(), n = p.length();
        boolean[][] dp = new boolean[m + 1][n + 1];
        dp[0][0] = true;
        for (int i = 0; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (p.charAt(j - 1) == '*') {
                    dp[i][j] = dp[i][j - 2];
                    if (matches(s, p, i, j - 1)) {
                        dp[i][j] = dp[i][j] || dp[i - 1][j];
                    }
                }else{
                    if(matches(s, p, i, j)){
                        dp[i][j] = dp[i-1][j-1];
                    }
                }
            }
        }

        return dp[m][n];
    }

    public boolean matches(String s, String p, int i, int j) {
        if (i == 0) {
            return false;
        }
        if (p.charAt(j - 1) == '.') {
            return true;
        }
        return s.charAt(i - 1) == p.charAt(j - 1);
    }
}
